Treatment of refractory zinc-lead ores.



. lead sulfate or other soluble it it in .5

K W n -furry l .ii li lq li TREATI/IENT OF REFRACTORY ZINC-LEAD GEES.

Specification of Letters Patent.

Patented June 15, 1909.

Application filed July 8, 1907. Serial No. 382,817.

To-cu wnom 2-K may concern.

Be it known that I, PERCY CLAUDE (Lin- ERON ISHERWOOD, Pb. D.,chemist, a subject of the King of Great Britain and li'elan .l, residing at The Oaks, l-ligh i'ioad, W aldstone, Harrow, England, have invented certain new to the Treatment of llel'actory Zincdieatl Ores, of which the following is a speciiication.

This invention relates to the treatment of refractory zinc-lead ores and has for its object to extract the zinc and copper with or without the lead and a portion of the silver from refactory sulfid or other ores in a simple and effective way and in a usable or salable form while leaving the gold and the remainder of the whole of the silver and lead in the residues ina form convenient for extraction by ordinary known means. According to the invention such ores are treated with ammonium sulfate suitably prepared as here after described for the solution of the bulk of the zinc and copper and a trace of the lea "l and for the subsequent precipitation thereof under conditions that do not involve the use of any other reagent and which permits of the regeneration of the ammonium sulfate.

The invention comprises the treatment of the ores in'the manner which is hereinafter described.

In carrying the invention into effect in the case, for example, pf sulfid ores, I grind the ore to a suitable degree of fineness and roast it in a current of air. In the case of ordinary refractory zinc-lead sulfid ores as those from the Broken Hill or similar deposits, the ore is ground to a convenient degree of fineness, such for examplefas to pass through sieve of from 90 to 100 meshes to the linear inch, and the roasting is advantageously started V at a very dull red heat, the ore being stirred the while to prevent caking. The heat is applied for two hours or more, the temperature being then increasedand the heating continued until practically no free sullid remains. Zinc, iron, copper and other oxidizable sulfids. which may be present are thus con verted, some wholly into oxids, some partly into sulfate and oxid and possibly some who ly into sulfate if the temperature happen to be exactlysuitable. The roasted ore may be then leached with water, whereby any zinc sulfates or compounds are dissolved out. The residues from the leaching or as the case may be the origil is produced and useful improvements lielatine" i l l l i with some zinc sulfa nal roasted ore, are treated in a hot concentrated solution of ammonium sulfate. The solution removed from the undissolved portion of the ore then contains a large proportion of the zinc and copper and a trace of the lead. (in cooling the solution and, if desired, diluting; with water the bulk of the zinc and traces of the lead are precipitated as double salts while the copper together with any excess of ammonium sulfate remains in solution. The bulk of the zinc and copper together with traces of the lead is dissolved out of the ore each as a double salt in combination with During the process, some free ammonia evolved and (zinc sulfate) consctpieritly produced. The ammonia may be separated and recovered by a method similar to that hm'einaftcr described. The evolution of ammonia may be reduced by conducting the extraction with the ammonium sulfate under pressure.

The zinc is extracted from the precipitate and the ammonia combined therewith is recovered as ammonium sulfate. 'lhe copper may be removed hour the solution. by any suitable means and the mother liquor which consists of an aqueous solution of the excess of ammonium sulfat a, and a pro 'iortion of the double salt or salts referral to together to, may be used. for the treatment of a further quantity of ore either alter or without eonrentration.

The solution of zinc sulfate obtained by the leaching of the roasted ore with water prior to the treat ment with ammonium sulfate may be treated by any suitable means for the extraction of the zinc either as metal or as sorbed in. sulfuric acid or condensed and subsequently neutralized with sulfuric acid. For the regeneration of. the ammonium sulfate solution thus produced a solution of calcium chlorid is added. Calcium sulfate is thereby precipitated and anunonium chlorid as a solution. This solution ammonium sulfate,

oxid or in any other form suitable for" sale as speltcr, pigmen t, etc.

after separation from the calcium sulfate and if necessary after concentration, is ready for treating a further quantity of ore. The solid. residues contain the zinc which was dissolved from i the ore by the ammonium sulfate together with calcium sulfate while the solution obtained by neutralinlng the ammoniacal distillate with sulfuric acid would be used for the extraction of successive quantities of ore, the calcium chlorid treatment being omitted. The solid residues aforesaid are treated by any suitable means for the recovery of the zinc in a salable form as metal or otherwise.

In the case of oxidized ores such as, for instance those containing calamin(zinc carbonatc) anglesite (lead sulfate) etc., the invention is carried out in exactly the same way, except that only sufficient roasting is re uired to convert carbonates into oXids.

t will be understood that the degree of extraction of the zinc depends largely on the care with which the roasting is carried out.

After prolonged heating at not too high a tem )erature, the process usually removes the ulk of the zinc, but when sufficient zinc remains in the residues to make its removal desirable it .may be extracted by hea ing the dried residue with a solid ammoniun sulfate at a temperature below redness, whereby the zinc and a proportion of the iron are converted into their respective sulfates with the simultaneous emission of ammonia gas.

The ammonia gas may be recovered by any of the usual processes and the sulfate of zinc and iron. dissolved out and recovered by any suitable means.

am aware that it has been proposed to treat the roasted ores with ammonium sulfate or ammonium sulfamate in -closed vcssels heated to from 300 to 500 C. for dissolving the zinc or copper as sulfates with the evolution of ammonia, which sulfates are af necessary the use of a closed vessel the term pera'ture being always at or underthe boiling point of the solution. while moreover it is the mo'nium sulfate, and then heating the resiessential purpose of my invention to produce and isolate a double compound of zmc oxid and ammonium sulfate and not zinc sulfate.

What I claim as .mv invention and desire to secure by Letters Patent" is 1. A process for extracting zinc and coper from refractory zinc lead ores consisting W 7 1n washing the ore and then treat1ng 1tm a concentrated solution of ammonium sulfate:

2. A'Tprocess for extracting zinc and copper from refractory zinc lead ores consisting in roast-mg the ore, 'leachlng 1t and thertreating the residue in a concentrated solution of ammonium sulfate.

,3. A process for extracting zinc and cop} per from refractory zinclead ores consisting in washing the ore and then treating it n a hot concentrated solution of ammonium sulfate. k

4. A process for extracting zinc and cop,-; per from refractory zinc lead ores consisting in roasting the ore, leaching it and then treating the residue in a hot concentrated soluiion of ammonium sulfate. l

5. A process for extracting zinc andcopper from refractory zinc lead ores consisting in Wasoing the ore, treating it 1n a concentra ed solution of ammonium sulfate and tlr heating the residues with solid ammonium sulfate at atemperature below redness 6. A process for extracting zinc and copper from refractory zinc lead ores consisting 1n roasting the ore, leaching it, treating the residues in a concentrated solution of ammonium sulfate, and then heating the residues with solid ammonium sulfate at. a tempera: ture below redness.

7. A process for extracting zinc and cop per'from refractory zinc lead ores consisting in washing the ore, treating it in a hot eoncentratedsolution of ammonium sulfate and then heating the residues with solid ammonium sulfate at a temperature below redness.

8. A pr ncess for extracting zinc copper from refractory zinc lead ores consisting in roasting the ore, leaching it, trcatin the residues in a hot concentrated solution 0 am- 105 dues with. solid ammonium sulfate at a term perature below redness.

In testimony whereof I have hereunto signed my name to this specification in the presence of two subscribin witnesses.

PERCY O. O. SHERWOOD.

Witnesses:

FREDERICK COLLINS RICHARD WILLIAM- 15mins. 

